Disambiguates some units. (#19875)

* Disambiguates some units.

* Updates DB attribute.

* Updates some more error-prone units.

* Updates some tests with legible constants.

* Updates query for MySQL case sensitivity.

* Fixes more casing issues.

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

api4/team.go

@@ -1501,7 +1501,7 @@ func getTeamIcon(c *Context, w http.ResponseWriter, r *http.Request) {
 	}
 
 	w.Header().Set("Content-Type", "image/png")
-	w.Header().Set("Cache-Control", fmt.Sprintf("max-age=%v, private", 24*60*60)) // 24 hrs
+	w.Header().Set("Cache-Control", fmt.Sprintf("max-age=%v, private", model.DayInSeconds)) // 24 hrs
 	w.Header().Set(model.HeaderEtagServer, etag)
 	w.Write(img)
 }